I concur with all of the ...

I concur with all of the previous comments.  However there is an alternative to sand filtration, which is called AFM (Active filtration media).  It is a treated coating on recycled glass with particle sizes approximately the same size as sand.  The difference is that the media does not become clogged because bacteria do not grow on the surface of the media.  It is backwashed using water.  I have been using it for 15 years successfully.  The comments of COD from this grey water still stand, but this will remove suspended materials and a significant level of bacteria.